Method for coppering of seamless tubes



June 21, 1938.

M. BRAUN METHOD FOR COPPERiNG OF SEAMLESS TUBES Filed NOV. 18, 1935 In ventof:

I M ai'tla'z'us Brawn Attorney I Patented June 21', 1 938 uurran STATES PATENT-1 or-Free Mn'rnon roncorranma or smmu'ss r runes 1 Matthias Braun, Frankl'ort-on-the-ltiaing Germany -Applicatlon November 18, '1935, Serial No. 50,450 f In GermanyJuly 4,1935

6 Claims.

between the anode and the wall of the tube would- 10 be too small.

1.6 The invention'isillustrated.on the accompanying drawing in whichi I Figural is a cross-sectional view or the steel tube with the copper coils therein and thereon,

Fig. 2 is a longitudinal sectional view of the g tube of Fig. 1, and Fig. 3 is a diagrammatic side view of the coppering apparatus. j

According to thepresent invention a specially prepared steel tube is coated with copper in 'a melting furnace. The preparation consists, ac-

' cording to Fig. l, in inserting a helically wound copper wire I) in the steel tube a to be coppered. r This wire of round cross section has its coils of outer diameter equal to that of the interior diam- 3' eter of the steel tube. It is wound helically in order that it may be applied over its whole length closely against the inner wall oi the steel tube and thus produce an uninterrupted metallic con tact with the tube wall. In this manner during. 35 the melting operation 01' the furnace, the copper will flow insuch a manner that it will uniformly coat the whole inner wall of the steel tube because during the liquefying of the copper, close contact with'the steel tube wall is. ensured at 40' every place. If the outerwall of the tube is to be coppered, a similar procedure is adopted. This The tube thus prepared is now brought into a furnace which has the melting temperature 55 of'copner and which preferably contains a reducing atmosphere to avoid burning or oxidation. According to the thickness of the copper wire, the copper deposit may be increased or decreased whereby a thicker or a thinner coppering is obtained. The copper layer may thus have its thickness regulated by choosin'g'a' thinner or a thicker wire or by arranging the coilsof the wire closer or farther apart. If an extremely" scanty or thinner copper coating is desir ed,'the steel tube is traversed through the furnace in an oblique'plane. 10 The copper wire liquefies and flows sothat the whole wall surface,. the inner orthe outerwall, of the steel tube is uniformly coated and brought into close metallic contact with the copper. Only so much'copper adheresto the wall. as correl5 sponds to the adhesion, of the metals.-- The excess material owingtothe oblique position of the tube flows downwards and away at thclower end of the same. In this manner an extremely thin metal coating is obtained. z

In this process it must be-taken intoconsideration that it is possible for a few'porous places, even if very small ones, toform on the surface, for example by developmentof bubbles. To remove these the tube is-subsequently subjected to a cold drawing operation; The coppered tube after cooling is thus drawn from a larger to a smaller diameter and the copper coating is compressed molecularly in such a manner that it undergoes a'compacting of its; surface which uniformly distributes the copper molecules and eliminates'porousplaces.

This process can be' further'improvedby giving the tube a rotarymovement during the melting operation in the furnace. The tube should be rotated about its longitudinal axis.-

By this rotation the metal of the copper wire helix inserted in thesteel tube and brought to the melting point in the muffle of the melting 4o furnace, is impelled against the inner wall of the tube and pressed against the same. The copper will be thereby distributed very uniformly and very finely over the whole inner wall. The centrifugal action obtainedby the rotation of the tube thus has the advantage that the flow of the copper from the tube wall takes place more uniformly and that the coating is denser. In particular, the rotary movement prevents accumula- I -tion of excessmolten copper at thelower end of the tube, owing to. its oblique position, which would give a thicker coating at this end.

The speed of rotation of the tube'in this operation is preferably between 1500-2000 revolutions per minute.

The finished copper tube can then be drawn as before toa smaller diameter.

In Fig. 3, the steel tube A which may be placed in any suitable position, is advanced obliquely through the muilie or chamber B of the furnace C in which it is to be coppered. It is not essential that the position should be oblique, it may be horizontal, but the oblique position is preferred. The copper wire helix is inserted into them-- terior of the tube. The tube A is given a rotary movement from the motor D. This motor is mounted on a slide F which is given a feed movement by. means of a screw spindle or shaft G driven by a motor E. The tube while retaining its oblique position is thus advanced through the furnace with a speed which corresponds to the time required for the satisfactory melting of the copper in the chamber B. On its issue from the melting furnace, the copper tube is received upon suitable guide means, and withdrawn.

By suitable selectionof the diameter of the copper wire helix and the number of its coils it is possible to determine with great precision the amount of copper required to produce .a satisfactory copper coating, of any desired thickness. Instead of the illustrated lathe mechanism for feeding and rotating the steel tube, other means for this purpose may be employed. For example, a whole series of. tubes may be operated by rollers or sets of rollers some of which effect the feed movementwhile others effect the rotary movement.

It is of course understood that solid bars may be copperedin the same manner as tubes by first applying a copper wire helically around the outside of the bar and then passing this barwith the wire thereon through the furnace. It is further to be understood that the process can be applied to any metallic article other than a tube and that any coating metal or alloy other than copper can be utilized as well as any melting method can be applied. Therefore, while the invention particularly concerns tubes, it is however understood that any metallic article may be coated provided the coating is carried-out by applying the metallic wire closely or in intimate contact with the surface to be coated.

I claim as my'in'vention:

1. A process of internally coppering tubes and the like comprising inserting in the tube copper wire wound in a helix oil-such diameter that the wire presses elastically along its whole length against the inner wall. of the tube, applying-a liquid flux to. the tube and the wire: helix wherein the flux will 'be retained. to agreater amount around the wire'ofthe helix, and subjecting the tube with the wiretherein to heat'to melt the copper and thus coat the inner wall.

2. A process'of internally coppering tubes-and the like comprising inserting-in the tube=copper wire wound in a helix with widely spaced coils and of such diameter that the wire presses elastically along its whole length against the inner wall of the tube, applying a liquid flux to the tube and the wire helix wherein the flux will be retained to a greater amount around the wire of the helix, and subjecting the tube with the wire therein to heat tomelt the copper and thus coat the inner wall.

3. A process of internally coppering tubes and the like comprising inserting in the tube copper wire wound in a helix of such diameter that the wire presses elastically along its whole length against the inner wall of the tube, applying a liquid flux to the tube and the wire helix wherein the flux will be retained to a greater amount around the wire of the helix, subjecting the tube with the wire therein to heat to melt the copper and thus coat the inner wall, and rotating the tube about its longitudinal axis during heating.

4. A process of internally coating metal tubes and the like with a liningof metal more fusible than that of the tube comprising inserting in the metal tube a wire of the more fusible metal wound in a helix the coils of which are at all points in self sustaining contact with the inner wall of the tubes, applying a liquid flux to the tube and the wire helix wherein the flux will be retained to a greater amount around the wire of the helix, and subjecting the tube with the wire-therein to heat suflicient to melt the wire and thus coat the inner wall with the more fusible metal.

5. A process of internally coating metal tubes and the like with a lining of metal more fusible than that of the tube comprising inserting in the metal tube a wire of the more fusible metal wound in a helix with widely spaced coils and the coils of which are at all points in self sustaining contact with the inner wall of the tube, applying a liquid fiux to the tube and the wire helix wherein the flux will be retained to a greater amount around the wire of the helix, and sub- :jecting the tube with. the wire therein to heat sufficient to melt the wire and thus coat the inner Wall with the more fusible metal.

6. A process of internally coating metal tubes and the like with a lining of metal more fusible than that of the tube comprising inserting in the metal tube a, wire of the more fusible metal wound in a helix thecoils of which are at all points in self sustaining contact with the inner wall of the tube, applying .a liquid flux to the tube and e the wire helix wherein, the flux will be retained to a greater amount around the wire of the helix, subjecting the tube with the wire therein to heat sumcient to melt the wire and thus coat the inner wall with the more fusible metal, .and rotating the tubeabout the longitudinal axis.

mr'miius BRAUN. 

